Assembly style

This post explains how I style 6502, 65c02 or 45gs02 assembly language. In addition, standard patterns translated to assembly can be found in Patterns in assembly language .

The examples are in Kick Assembler format.

Code Layout §

Instructions §

• instructions are in lowercase.
• instructions are tabbed 16 chars to the right.

Labels §

• labels do not override the instruction space, max length is 14.
• labels are on the same line as the first instruction.

Comments §

• comments explaining a block of code are positioned at the beginning of the line.
• comments explaining an instruction are positioned after the instruction.

Example

// this is a comment explaining
// the following code block in a general way.

  			lda #01
  			sta $d020
  			ldx #$00          // reset string index
!:		        lda string,x
  			beq done
  			jsr $ffd2
  			inx
  			jmp !-
  			
done:		    jsr PRIMM
  			.text "THIS IS IMMEDIATE PRINT."
  			.byte 0
  			jmp *
  			
.string:        .text "HELLO WORLD"
  			.byte 13, 0

Subroutines §

Must explain:

• *function: one or two words naming the function
• input: which registers must be set, and what do they contain?
• output: which register is set with what return information?
• destroys: which registers are destroyed when running this routine?
• calls: which other routines are called from this one?
• description: more in-depth explanation of the function.

// ***************************************
// * FUNCTION: Initialize Interrupts
// * INPUT: rasterline to trigger interrupt in .A
// * OUTPUT: none
// * CALLS: none
// * DESTROYS: .X, .Y
// * DESCRIPTION: sets up a raster interrupt at passed line

Operations §

Binary §

Binary operations use binary notation for clarity:

				lda #%10000000    // clear bit 7
				trb $d015